lIn the modified win.env.bat file, I added @set PROCESSOR_ARCHITECTURE=x86 to line 106 to get it to build under AMD64. The build environment was X86 already, but apparently it wasn't enough.

lOn line 144 of the modified tools\nmake\def.mak file, comment out #CFLAGS = $(CFLAGS) -Wp64, since the flag is deprecated.

lThis one didn't seem right, but it was the most expedient: comment out lines 73 to 79 in pal\exception.c, which is the declaration of a function RtlUnwind which is apparently never used or defined. It could be some platform specific call, which works on a Windows machine.